Building structures, particularly tall urban buildings, are typically washed manually. A scaffolding structure is usually suspended from the top of the building to be washed. The scaffolding can be raised or lowered so that a person standing on the scaffolding can wash the windows and exterior surfaces of the building by hand. After a vertical section of the building is washed, the scaffolding is repositioned laterally so that the next adjacent vertical section of the building may be cleaned. This procedure may be repeated until the entire building has been washed. Cleaning windows using scaffolding is extremely time consuming. In an effort to reduce time and cost, therefore being more competitive in the industry, window washers tie a climbing rope to the roof anchors provided for the scaffolding and throw the rope over the side of the building. Then they attach a bosons chair to the rope and a climber's harness to themselves with repelling hardware. The man goes over the side of the building with his tools and water/soap bucket and cleans 6-8 of horizontal glass width per story. Then repels down to the next level and repeats until that drop is complete.
Manual washing of buildings has proven to be quite dangerous, especially with respect to tall skyscrapers. Typical wind and air drafts surrounding a building can exert a significant aerodynamic force upon a scaffolding structure or window cleaning laborer, causing them to swing out and away from the building, and placing persons standing on that scaffolding or suspended on a rope in peril. Injuries from manual window washing operations are common, and have caused insurance rates to soar. Typically, the cost of insuring a window washing operation can reach 40% of the labor costs. Furthermore, the manual washing of building exteriors is slow and labor-intensive.
Effectively removing mineral deposits from building windows has been a problem which has long plagued the industry. Normal water supplies conventionally used for wash water contain some amount of dissolved solids, including calcium, magnesium, and sodium in the form of bicarbonates, carbonates, chlorides, or sulfates. Regardless of the type or form of the dissolved solids, when a water droplet is allowed to dry on a surface, the solids typically remain as deposits on the surface.
When washing a window, a single water drop left on the surface will typically contain between 300 and 1000 parts per million of dissolved solids, in addition to varying amounts of suspended solids removed from the surface by washing. When water drops evaporate, mineral deposits are left in “spots”. Compounding the spotting problem is the fact that when a window is being cleaned in sunlight, the surface of the window can be elevated to as much as 120 degrees F. Wash water in such circumstances evaporates quickly and can be seen to “steam” off of the window. Heavy and ultimately damaging mineral deposits can result.
Surface active agents (i.e. cleaning agents), such as polyphosphate and organic detergents, serve to spread adhering water drops over a wider area, making water spotting less noticeable. However, the effect is only cosmetic as the accumulation of hard mineral deposits as a whole is unaffected.
Although various automatic window washing devices have been described in the art (see, for example, U.S. Pat. Nos. 3,344,454 and 3,298,052), the inventor is not aware of any such devices which have proven to be practical or accepted in use. Such devices typically employ mechanical techniques to scrub the surface and to remove residual water. These cleaners suffer from a combination of several problems. First, many require some form of tracking (e.g., vertical mullions) on the building facade to guide the device up and down and maintain cleaning contact with the surface. Second, many include elaborate mechanical water collection and liquid removal apparatus, adding weight and expense to the overall device. Finally, since it is difficult to completely remove all of the wash water from the surfaces, and since all devices known to the inventor use common tap water (with or without detergents) as the washing medium, they tend to clean ineffectively, leaving mineral deposits from the tap water itself.
It is desirable to use unmanned, self-propelled vehicles such as robots to perform a variety of functions that would be difficult or dangerous for a person to perform. For example many people frequently use robots to retrieve or dispose an explosive device or inspect or work in an environment that could kill or injure a person. People also frequently use robots to inspect or work in locations that typically are hard to access or are inaccessible by a person such as inspecting a pipeline.
Unfortunately, because robots typically propel themselves to a work site, use of most conventional unmanned, self-propelled vehicles is typically significantly limited by the ability of the robot to propel itself over a surface. For example, surfaces that include compound curves or three dimensional curves, abrupt inclinations or declinations, steps or gaps can cause conventional robots to become significantly less stable, i.e., more likely to lose their preferred orientation relative to the surface, as they traverse the surface or turn on it. In addition, surfaces that are slippery can cause conventional robots to easily lose a significant portion, if not all, of their traction to the surface. If either happens while traversing an incline or inverted surface such as a ceiling, such a loss of traction could cause the robot to fall. Such a fall could seriously damage the robot, its payload if it has any, or the surface or other components of the structure the robot is traversing.
Another problem with conventional robots is they tend to scrub the surface as they traverse and turn on it. This can cause undesirable scratches on the surface. For example, the exterior surface of the glass may have a reflective or solar coating or film that is more easily scratches than the glass.
Yet another problem with conventional robots is they tend to bounce or jerk as they propel themselves across a surface. This can be a significant problem during use on glass surfaces.
U.S. Pat. No. 5,249,326 discloses a washing system comprising a cleaning device for cleaning exterior surfaces of buildings, means for suspending the cleaning device in contact with the building surface to be cleaned, and means for causing the washing unit to traverse the building surface to be cleaned. Means for restraining the cleaning device against the building surface to be cleaned are provided, said restraining means including a restraining cable having a free weight attached thereto, means for attaching the restraining cable to the building at a point above the cleaning device, and a member for attaching the restraining cable to the building at a point below the cleaning device, the member being mounted on a suction cup adapted to engage the building. In use, the restraining cable is attached to the building at a point above the cleaning device, then passes over the cleaning device, and is threaded through the member below the cleaning device, such that the free weight hangs below the member and exerts a downward force on the cable, and the cable thereby restrains the cleaning device against the building surface to be cleaned. Preferably, the member connected to the suction cup comprises a pulley. Alternatively, it may be a loop, a U-shaped piece, or any other structure having a bore or passage through which the restraining cable can pass.
U.S. Pat. No. 5,890,250 describes a robotic apparatus for applying fluids to the exterior surfaces of vertical, nearly vertical, or sloped surfaces with minimum human supervision. The robotic apparatus is designed to apply fluids to surfaces which may include obstacles such as window frames or gaps created by window seams, which the present invention is designed to traverse. The robotic apparatus includes housing, a drive assembly, a sliding vacuum assembly, a fluid spray assembly, and sensor and control systems. The drive assembly includes drive chains, cables, ropes or the like that are connected at one end to a carriage positioned on the top of the structure and to a stabilizing member or members at the other end.
U.S. Pat. No. 5,707,455 describes an automated cleaning method is provided for an exterior wall of a building. Elongated, water-tight or electrically-insulating hollow members are accommodated within upper and lower sash rails constructing said exterior wall so that said hollow members continuously extend in horizontal directions, respectively. An electrical conductor extends in one of the hollow members. The other hollow member forms a drainage system. A cleaning apparatus main unit is arranged so that said cleaning apparatus main unit is supplied with electric power through said conductor to permit self-traveling in a horizontal direction along said exterior wall and is also supplied with washing water from said drainage system to permit cleaning of a surface of said exterior wall. The washing water is drained into said drainage subsequent to the cleaning by said cleaning apparatus main unit. The washing water can be recirculated for reuse.
U.S. Pat. No. 5,014,803 describes a device, including a window cleaning device, comprising a main body, a motor and drive wheels mounted on the main body, a partitioning member mounted on the main body and defining a pressure reduction space in cooperation with the main body and a wall surface, and a vacuum pump for reducing the pressure of the pressure reduction space. The device can suction-adhere to the wall surface by the pressure of an ambient fluid acting on the main body owing to the difference in fluid pressure between the inside and outside of the pressure reduction space and move along the wall surface by the action of the moving member. The partitioning member has an outside wall portion extending from its one end to a contacting portion contacting the wall surface and an inside wall portion extending from the contacting portion to its other end. A stretchable and contractible portion is provided in at least one of the outside and inside wall portions, and the contacting portion moves toward and away from the wall surface by the stretching and contracting of the stretchable and contractible portion.